STM32 LoRa Telemetry Relay System

A robust firmware project for a dual-node STM32 NUCLEO-WL55JC1 system designed to capture, validate, and retransmit data from a radiosonde via LoRa for long-range telemetry. This project was developed as a technical study in embedded systems and wireless communication.

Key Features

• Robust Hardware Platform: Utilizes two STM32 NUCLEO-WL55JC1 development boards, which integrate a powerful microcontroller and a LoRa transceiver on a single chip.
• Efficient Firmware: Employs DMA in circular mode for non-blocking UART data reception from the radiosonde, freeing up the CPU for other tasks.
• Reliable Data Parsing: A Finite State Machine (FSM) validates incoming data packets using a SYNC_WORD and checksum to ensure data integrity before retransmission.
• Low-Power, Event-Driven Receiver: The base station is fully interrupt-driven, operating in a low-power sleep mode until a LoRa packet is received, making it highly efficient.
• Layered Software Architecture: The firmware is built on STMicroelectronics' HAL (Hardware Abstraction Layer) and BSP (Board Support Package), ensuring clean, portable, and maintainable code.

Project Structure

The repository is organized into a clean, modular structure:

/
├── README.md
├── src/
│   ├── Field_Node/
│   ├── Base_Station/
│   └── common/
│       └── protocol.h
├── docs/
│   ├── Relatorio_Tecnico.pdf
│   └── images/
└── .gitignore

System Architecture

The system consists of two main nodes that work in tandem:

1. Node 1: Field Node (Transmitter)

   • Connects directly to a radiosonde via USART1 (19200 baud) to capture a continuous stream of telemetry data.
   • Parses the data stream using an FSM to identify and validate complete data packets.
   • Valid packets, verified by a checksum, are transmitted wirelessly using the onboard LoRa radio.

2. Node 2: Base Station (Receiver)

   • Acts as a LoRa gateway, remaining in a continuous reception mode.
   • Upon receiving a valid LoRa packet, it decodes the binary payload into human-readable data.
   • Sends the formatted data to a connected PC via a Virtual COM Port (USART2 at 115200 baud) for real-time monitoring.

LoRa Communication Parameters

To ensure a robust and long-range communication link, the following LoRa parameters were configured for both nodes:

Parameter	Value
Frequency	915.0 MHz
Spreading Factor (SF)	10
Bandwidth (BW)	125 kHz
Coding Rate (CR)	4/8
Transmission Power	22 dBm
Packet Mode	Fixed Size (Implicit Header)

How to Use

1. Hardware Required:

   • 2x STM32 NUCLEO-WL55JC1 development boards
   • 2x 915 MHz Antennas
   • A radiosonde or other serial data source (19200 baud)

2. Setup:

   • Clone this repository.
   • Open STM32CubeIDE and import the two projects located in src/Field_Node/ and src/Base_Station/.
   • Compile both projects.
   • Flash the Field_Node firmware onto the first board and Base_Station onto the second.

3. Execution:

   • Connect the Field Node to the radiosonde.
   • Connect the Base Station to a PC and open a serial terminal (like PuTTY) on the corresponding COM port at 115200 baud to view the received telemetry data.

Validation & Results

The system was fully tested, demonstrating a successful end-to-end communication link. The following are sample outputs captured from the serial terminals of both nodes during a test run.

Transmitter (Field Node) Terminal Output:

Checksum OK. Pacote da radiosonda validado.
Transmitindo pacote LoRa ID: 1
LoRa TX Done.

Receiver (Base Station) Terminal Output:

Pacote LoRa Recebido! RSSI: -50 dBm, SNR: 9

---[ PACOTE DE TELEMETRIA DECODIFICADO ]---
ID do Pacote: 1
Latitude:     -3.740123
Longitude:    -38.570456
Altitude:     50.12 m
Voltagem:     3300 mV
Temp. Radio:  25 C
Status GPS:   FIX OK (Satelites: 8)

Future Work & Roadmap

This project serves as a solid foundation for a field-ready telemetry system. Recommended next steps include:

• Power Optimization: Implement the final low-power sleep modes (SUBGRF_SetSleep) on the Field Node to maximize battery life.
• Data Visualization: Develop a GUI or logging script on the PC to better visualize, store, and analyze the incoming telemetry data.
• Field Testing: Conduct real-world, open-field range tests to validate the performance and maximum range of the LoRa link.
• Bi-directional Communication: Implement a command system to send configuration messages from the Base Station back to the Field Node.

Authors

• Alisson Jaime Sales Barros
• Danilo Mota Alencar Filho